The present invention relates to instruments for obtaining tissue samples to be used for example in biopsy procedures. More particularly, the invention relates to improved instruments for propelling needle assemblies in the diagnostic tissue sampling operation.
In the effort to improve diagnostic tissue sampling, particularly of prostate tissue, needle assemblies have been developed which capture longitudinal, or core sample of the tissue which is extracted for diagnosis. Conventionally, a two-part needle assembly having an outer cannula and inner stylet are employed to cut and capture a core of the tissue as described for example in U.S. Pat. No. 4,776,346. Such instruments have been improved to enable relative propulsion of the two-parts of the needle assembly employing a drive carriage within the instrument which is propelled by a single drive spring expanded and compressed with reversible motions which are conveniently operated manually by the physician as described in U.S. Pat. No. 5,121,751, the disclosure of which is incorporated by a reference for complete description of the needle drive mechanism and operation. These instruments can be provided with improved arming and activation arrangement with safety lock-out structure, in accordance with the present invention.